Package org.orekit.data

Interface DataFilter

All Known Implementing Classes:
GzipFilter, HatanakaCompressFilter, NsgfV00Filter, TruncatingFilter, UnixCompressFilter
public interface DataFilter
Interface for filtering data (typically uncompressing it) in data providers before passing it to data loaders.
Since:
9.2
Author:
Luc Maisonobe
See Also:

  • Method Summary

    Modifier and Type
    Method
    Description
    DataSource
    filter(DataSource original)
    Filter the data source.

  • Method Details

    • filter

      DataSource filter(DataSource original) throws IOException
      Filter the data source.

      Filtering is often based on suffix. For example a gzip compressed file will have an original name of the form base.ext.gz when the corresponding uncompressed file will have a filtered name base.ext.

      A filter must never open the DataSource by itself, regardless of the fact it will return the original instance or a filtered instance. The rationale is that it is the upper layer that will decide to open (or not) the returned value and that a DataSource can be opened only once; this is the core principle of lazy-opening provided by DataSource.

      Beware that as the data providers manager will attempt to pile all filters in a stack as long as their implementation of this method returns a value different from the original parameter. This implies that the filter, must perform some checks to see if it must be applied or not. If for example there is a need for a deciphering filter to be applied once to all data, then the filter should for example check for a suffix in the name and create a new filtered DataSource instance only if the suffix is present, removing the suffix from the filtered instance. Failing to do so and simply creating a filtered instance with one deciphering layer without changing the name would result in an infinite stack of deciphering filters being built, until a stack overflow or memory exhaustion exception occurs.

      Parameters:
      original - original data source
      Returns:
      filtered data source, or original if this filter does not apply to this data source
      Throws:
      IOException - if filtered stream cannot be created